Multiphysics modeling of particle spattering and induced defect formation mechanism in Inconel 718 laser powder bed fusion

Powder particle spattering induced by the metal vapor jetting and vortex flow near the melt pool significantly influences the porosity of final product. In this work, a high-fidelity multiphysics model is developed at powder-scale that unidirectionally couples the powder spattering and laser welding simulation to study the spattering and porosity formation mechanism in laser powder bed fusion process. Vapor pressure from single-track laser welding simulation is applied as a moving boundary condition in a discrete element model to simulate particle spattering. Then, coupling simulation between the mass particles and laser welding is performed to study the interaction between melt pool and spattering particles. Two porosity formation mechanisms are observed in experiments and simulation. The first one is the spattering particles falling into melt pool directly and leaving un-melted or partially melted pores to the final product. The second mechanism is the particles near the melt track that are dragged to the melt pool bead and partially melted due to heat conduction. These partially melted particles can be observed as well in the bead region of depositions.